Gas filters are used in a variety of assemblies and systems. For example, it is desirable to filter intake air to a variety of vehicles and other equipment. Typically, the intake air is combustion air for an internal combustion engine, often a diesel engine. Filtration is generally conducted with a gas (air) cleaner assembly (i.e. a filter assembly) typically including a housing and an internally positioned filter cartridge arrangement. The filter cartridge arrangement typically includes a main filter cartridge, through which the air is passed and which is operated with deposition of particulate material carried therein onto filter media of the main filter cartridge. In a variety of air cleaner assemblies, the main filter cartridge and the remainder of the assembly are configured for out-to-in flow during filtering, in reference to direction of air flow through the media of the main filter cartridge, during normal operation. When this is the case, the media of the main filter cartridge is typically configured surrounding an open filter interior that is a clean air side of the media.
In many instances, a safety or secondary filter cartridge is included within the filter assembly. When a safety or secondary filter cartridge is used with an assembly configured for out-to-in flow during filtering, the safety filter is typically configured with media thereof surrounding an open filter interior and projecting into an open filter (clean gas) interior of the main filter cartridge. Thus, after the gases (air) pass through the media of the main filter cartridge, the gases (air) pass through the media of the safety filter cartridge as those gases (air) are directed toward an outlet from the air cleaner.
In a typical assembly, both the main filter cartridge and the safety filter cartridge are configured as service components. That is, they are configured to be removable from, and to be replaceable within, the air cleaner assembly. As a result, each is generally provided with releasable housing seal, i.e., a seal which removably seals to a portion of the housing or air cleaner assembly, when the two filter cartridges are properly and operably positioned. Such seals are sometimes referred to as “releasable seals” since they can be established and be removed without damage to the cartridges or housing component(s) engaged.
A variety of assemblies have been developed which can use such general arrangements. Examples are described in WO 2009/014986 A1 and WO 2012/116314 A1, each which is incorporated herein by reference and which are owned by the owner of the present disclosure, Donaldson Co., Inc., of Bloomington Minn.
Issues relating to the safety or secondary filter cartridge configuration concern limitations in its size and shape imposed by the requirements of the gas filter assembly for location of the safety filter, typically enclosed within the main filter cartridge yet still meant to be removably sealed to a feature of the air cleaner assembly or housing; and the preferred desire to be able to service the main filter without dislodging the safety. Improvements have been sought.